J Plant Ecol ›› 2016, Vol. 9 ›› Issue (6): 752-761 .DOI: 10.1093/jpe/rtw015

• Research Articles • Previous Articles     Next Articles

Source of inorganic N affects the cost of growth in a legume tree species (Virgilia divaricata) from the Mediterrean-type Fynbos ecosystem

Anathi Magadlela1, María A. Pérez-Fernández2,*, Aleysia Kleinert1, Léanne L. Dreyer1 and Alex J. Valentine1   

  1. 1 Botany and Zoology Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; 2 Deparment of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
  • Received:2015-10-16 Accepted:2016-02-12 Published:2016-12-02
  • Contact: Perez-Fernandez, Maria

Source of inorganic N affects the cost of growth in a legume tree species (Virgilia divaricata) from the Mediterrean-type Fynbos ecosystem

Abstract: Aims In Mediterranean-type ecosystem, the Cape Fynbos, legumes may be able to switch between soil N and atmospheric N 2 sources during growth to adjust the carbon costs of N acquisition. This study investigated the utilization of different inorganic N sources by Virgilia divaricata, a native legume from the Mediterranean-type ecosystem of the Cape Floristic Region.
Methods Plants were cultivated in sterile quartz sand, supplied with 25% strength Long Ashton nutrient solution, modified to contain 500 μM Phosphate. At the phosphate level (500 μM), plants were treated with 500 μM NH 4 NO 3 (treatment named N), or grown in N-free nutrient solution and inoculated with effective Burkholderia sp. (Bact.) or treated with combined N sources (500 μM NH 4 NO 3) and inoculated with effective Burkholderia sp. (N+Bact.).
Important findings The application of NH 4 NO 3 to the legumes resulted in a greater increase in plant dry matter. Carbon construction costs were higher in plants that were supplied with mineral and symbiotic N sources. Maximum photosynthetic rates per leaf area was maintained, irrespective of the N sources. Although the plant roots were nodulated, the plant dependence on N 2 fixation decreased with addition of N. Roots and nodules of the plants solely reliant on N 2 fixation showed an increase in glutamine content. These results show that V. divaricata is highly adapted for growth at the forest margin. Fynbos and possibly anthropic soils by utilizing both atmospheric and soil N sources.

Key words: phosphate deficiency, Virgilia divaricata, N2 fixation, mineral N, C construction costs, asparagine

摘要:
Aims In Mediterranean-type ecosystem, the Cape Fynbos, legumes may be able to switch between soil N and atmospheric N 2 sources during growth to adjust the carbon costs of N acquisition. This study investigated the utilization of different inorganic N sources by Virgilia divaricata, a native legume from the Mediterranean-type ecosystem of the Cape Floristic Region.
Methods Plants were cultivated in sterile quartz sand, supplied with 25% strength Long Ashton nutrient solution, modified to contain 500 μM Phosphate. At the phosphate level (500 μM), plants were treated with 500 μM NH 4 NO 3 (treatment named N), or grown in N-free nutrient solution and inoculated with effective Burkholderia sp. (Bact.) or treated with combined N sources (500 μM NH 4 NO 3) and inoculated with effective Burkholderia sp. (N+Bact.).
Important findings The application of NH 4 NO 3 to the legumes resulted in a greater increase in plant dry matter. Carbon construction costs were higher in plants that were supplied with mineral and symbiotic N sources. Maximum photosynthetic rates per leaf area was maintained, irrespective of the N sources. Although the plant roots were nodulated, the plant dependence on N 2 fixation decreased with addition of N. Roots and nodules of the plants solely reliant on N 2 fixation showed an increase in glutamine content. These results show that V. divaricata is highly adapted for growth at the forest margin. Fynbos and possibly anthropic soils by utilizing both atmospheric and soil N sources.